CN115770878A - Method for reducing anisotropy of mechanical properties of high-strength titanium alloy manufactured by additive manufacturing - Google Patents
Method for reducing anisotropy of mechanical properties of high-strength titanium alloy manufactured by additive manufacturing Download PDFInfo
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- 229910001069 Ti alloy Inorganic materials 0.000 title claims abstract description 94
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- 238000000034 method Methods 0.000 title claims abstract description 49
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 60
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- 229910052742 iron Inorganic materials 0.000 claims description 12
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- 239000012535 impurity Substances 0.000 claims description 6
- 239000010936 titanium Substances 0.000 claims description 5
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 4
- 238000011068 loading method Methods 0.000 claims description 4
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- 230000015572 biosynthetic process Effects 0.000 abstract description 6
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- Y02P10/25—Process efficiency
Abstract
The invention discloses a method for reducing anisotropy of mechanical properties of high-strength titanium alloy manufactured by additive manufacturing, which comprises the following steps: 1. adding iron powder into the spherical Ti185 alloy powder and ball-milling to obtain mixed powder; 2. drawing a three-dimensional model of a target product and carrying out layering processing to obtain slicing data and design slicing scanning data; 3. importing the layer cutting data and the layer cutting scanning data into equipment for powder filling, leveling a forming bottom plate and preheating; 4. laying and laying a powder layer and preheating; 5. melting and scanning to form a single-layer solid sheet layer; 6. and repeating the processes to form a powder bed electron beam additive manufacturing forming piece to obtain the high-strength titanium alloy. According to the invention, the powder bed electron beam additive manufacturing is carried out by adding the iron powder into the Ti185 alloy powder, so that the growth restriction factor and the solidification temperature interval value of the alloy are improved, the formation of equiaxed crystals in the titanium alloy is facilitated, the strength of the titanium alloy is improved, the anisotropy of the mechanical property of the titanium alloy is reduced, and the titanium alloy is used as a high-strength component and has a wide application range.
Description
Technical Field
The invention belongs to the technical field of alloy material preparation, and particularly relates to a method for reducing anisotropy of mechanical properties of high-strength titanium alloy manufactured by additive manufacturing.
Background
The titanium alloy has the advantages of high specific strength, good biocompatibility, corrosion resistance, no magnetism, heat resistance and the like, and is widely applied to the fields of biological medicine, aerospace, ocean engineering, petrochemical industry and the like. With the rapid development of aerospace industry, the conventional titanium alloy material is difficult to meet the requirements, so that the high-strength titanium alloy comes into the sight of people.
The titanium alloy has poor thermal conductivity, large deformation resistance, narrow forging temperature range, large affinity to oxygen and the like, so that the preparation of a titanium alloy sample piece has a plurality of difficulties. The powder bed electron beam additive manufacturing, also called as electron beam selective melting (SEBM), is an advanced manufacturing technology developed in the 90 s of the 20 th century, has the advantages of high scanning speed, no pollution to a high vacuum environment, low residual stress and the like, and is particularly suitable for direct forming of active metal materials such as titanium alloy and the like.
The Ti-1Al-8V-5Fe (Ti 185) alloy belongs to metastable beta titanium alloy, has higher tensile strength and shear strength, and is widely applied to aviation fasteners and parts with higher strength requirements. In addition, the alloy is lower in cost compared to other metastable beta titanium alloys. However, the Ti185 alloy is formed by powder bed electron beam additive manufacturing, and the inside of the alloy is a coarse columnar crystal structure along the forming direction, so that the anisotropy of the mechanical property of the alloy is obvious, and the problem seriously restricts the large-scale development, popularization and application of the powder bed electron beam additive manufacturing and the titanium alloy preparation thereof.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a method for reducing the anisotropy of mechanical properties of high-strength titanium alloy manufactured by additive manufacturing, aiming at the defects of the prior art. According to the method, the titanium alloy is prepared by adding iron powder to the Ti185 alloy powder and performing powder bed electron beam additive manufacturing, so that the growth restriction factor and the solidification temperature interval value of the alloy are improved, the formation of isometric crystals in the titanium alloy is facilitated, the beta/alpha transition temperature is reduced, the precipitation of a nano alpha strengthening phase of the titanium alloy is promoted, the strength of the titanium alloy is improved, and the anisotropy of the mechanical properties of the titanium alloy is reduced.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a method for reducing anisotropy of mechanical properties of high-strength titanium alloy manufactured by additive manufacturing is characterized in that the high-strength titanium alloy with isotropic mechanical properties is prepared by increasing the iron content in Ti-1Al-8V-5Fe alloy, namely Ti185 alloy powder and adopting powder bed electron beam additive manufacturing, and the method comprises the following steps:
step one, adding iron powder into spherical Ti185 alloy powder prepared by gas atomization of a plasma rotating electrode, and then carrying out ball milling by adopting a planetary ball mill to obtain mixed powder;
drawing a three-dimensional model of a target product titanium alloy, then carrying out layering treatment, cutting the three-dimensional model into equal-thickness slices along the height direction of the three-dimensional model, obtaining slicing data, and designing the internal scanning mode and scanning path of each slice to obtain slicing scanning data;
step three, guiding the layer cutting data and the layer cutting scanning data obtained in the step two into powder bed electron beam additive manufacturing forming equipment, loading the mixed powder obtained in the step one into a powder box of the powder bed electron beam additive manufacturing equipment, leveling a forming bottom plate and preheating the forming bottom plate, wherein the preheating temperature of the forming bottom plate is 700-720 ℃;
step four, laying the mixed powder loaded into the powder box in the step three on the preheated forming bottom plate to form a powder laying layer, and then preheating the powder laying layer, wherein the preheating temperature of the powder laying layer is 700-720 ℃; the thickness of the powder laying layer is the same as that of the sliced sheet layer in the third step;
step five, according to the layer cutting data and the layer cutting scanning data which are led into the powder bed electron beam additive manufacturing forming equipment in the step three, melting and scanning the preheated powder laying layer in the step four by adopting an electron beam to form a single-layer solid sheet layer, and then descending the forming bottom plate, wherein the descending height of the forming bottom plate is the same as the thickness of the sheet layer which is cut in the step four;
sixthly, repeating the powder laying process and the preheating process in the step four, and the melting scanning process and the forming bottom plate descending process in the step five until all the single-layer solid sheets are stacked layer by layer to form a powder bed electron beam additive manufacturing formed part, taking out the formed bottom plate when the temperature of the formed bottom plate is lower than 100 ℃, and removing residual powder on the surface of the powder bed electron beam additive manufacturing formed part by using high-pressure gas to obtain high-strength titanium alloy; the tensile strength of the high-strength titanium alloy in the horizontal direction is higher than 1317MPa, the tensile strength of the high-strength titanium alloy in the vertical direction is higher than 1303MPa, the tensile yield strength of the high-strength titanium alloy in the horizontal direction is higher than 1241MPa, the tensile yield strength of the high-strength titanium alloy in the vertical direction is higher than 1222MPa, the elongation after fracture is higher than 5%, and the strength anisotropy value is not higher than 1.5.
The method adopts spherical Ti185 alloy powder prepared by gas atomization of a plasma rotating electrode as a raw material, adds iron powder, performs ball milling and mixing to obtain mixed powder, and then prepares the high-strength titanium alloy with isotropic mechanical properties by powder bed electron beam additive manufacturing. Firstly, the sphericity of the spherical Ti185 alloy powder prepared by gas atomization of the plasma rotating electrode is high, the particle size of the spherical Ti185 alloy powder is suitable for powder bed electron beam additive manufacturing equipment, and the spherical powder is easy to spread uniformly in the additive manufacturing process, so that the structural uniformity of the Ti185 alloy is improved; secondly, the iron powder is added into the spherical Ti185 alloy powder, so that the growth restriction factor and the solidification temperature range of the alloy are increased, the formation of isometric crystals is facilitated, meanwhile, the iron is a beta stable element, the beta/alpha transition temperature of the alloy is reduced by increasing the iron content, the preparation is carried out by combining the powder bed electron beam additive manufacturing, the titanium alloy is facilitated to obtain finer strengthening phase alpha, and the anisotropy of the mechanical property of the titanium alloy is reduced; the ball-milling mixing of the spherical Ti185 alloy powder and the iron powder is carried out by adopting a planetary ball mill, so that the iron powder is favorably and uniformly distributed on the surface of the Ti185 alloy powder, and the component uniformity of the product titanium alloy is favorably improved; thirdly, in the powder bed electron beam additive manufacturing process, the forming bottom plate and the powder laying layer are preheated, and the preheating temperature is controlled to be 700-720 ℃, so that each prepared single-layer solid sheet layer is subjected to repeated heat treatment, the gradual release of the internal thermal stress of the titanium alloy product is facilitated, the internal structure of the titanium alloy tends to be uniform, meanwhile, the spherical Ti185 alloy powder on the powder laying layer is preheated and then melted and scanned, so that the powder is adhered, the powder laying layer movement caused by electron beam impact is avoided, the interlayer binding force of the titanium alloy is improved, the titanium alloy is prevented from generating component segregation, and particularly the segregation of Fe element generates beta spot defect, so that the strength of the titanium alloy is influenced.
The method for reducing the anisotropy of the mechanical properties of the high-strength titanium alloy manufactured by the additive manufacturing process is characterized in that in the first step, the spherical Ti185 alloy powder consists of the following components in percentage by mass: 1.38% of Al, 8.00% of V, 4.22% of Fe, 0.19% of O and the balance of titanium and inevitable impurities, and the particle size of the spherical Ti185 alloy powder is 40-150 μm. The spherical Ti185 alloy powder with the particle size has good fluidity, is beneficial to spreading of mixed powder on a forming bottom plate, improves the uniformity of a powder spreading layer, further improves the uniformity of each component in the product titanium alloy, and avoids the occurrence of composition segregation; meanwhile, the spherical Ti185 alloy powder with the grain diameter is beneficial to improving the melting speed in the powder bed electron beam additive manufacturing and forming process.
The method for reducing the anisotropy of the mechanical properties of the high-strength titanium alloy manufactured by the additive materials is characterized in that in the step one, the particle size of the iron powder is 1 mu m, and the addition amount of the iron powder is 1.89% of the mass of the spherical Ti185 alloy powder. By controlling the particle size of the iron powder, the iron powder is favorably and uniformly attached to the surface of the Ti185 alloy powder, and is not agglomerated. Generally, the iron content of the Ti185 alloy is 4-6% by mass, 1.89% of iron powder is added into the Ti185 alloy powder to prepare mixed powder according to a chemical element proportion calculation method, the iron content of the mixed powder is still within the component content range of the conventional Ti185 alloy powder, other impurity elements are prevented from being introduced, and the mechanical property of the titanium alloy is ensured.
The ball milling process of the invention comprises the following steps: adding iron powder into spherical Ti185 alloy powder prepared by gas atomization of a plasma rotating electrode, then placing the powder into a ball milling tank of a planetary ball mill, adding ball milling beads and ethanol into the ball milling tank, and carrying out ball milling for 4 hours at the rotating speed of 20r/min to obtain mixed powder. Ethanol is added in the process to promote the uniform adhesion of the iron powder on the surface of the spherical Ti185 alloy powder.
The method for reducing the anisotropy of the mechanical properties of the high-strength titanium alloy manufactured by the additive is characterized in that the thickness of the uniform-thickness sheet layer in the second step is 0.1mm. The thickness of the sheet layer is controlled to be 0.1mm so as to adapt to the melting capacity of the electron beam to the mixed powder.
The method for reducing the anisotropy of the mechanical properties of the high-strength titanium alloy manufactured by the additive is characterized in that the process parameters of melting and scanning in the fifth step are as follows: the distance between scanning lines is 0.1mm, the scanning current is 15mA, and the scanning speed is 3300mm/s. The titanium alloy is manufactured by performing powder bed electron beam additive manufacturing on the titanium alloy spherical powder by adopting the melting scanning forming parameters, the size precision and the melting quality of each sheet layer in the forming process are effectively controlled, the prepared titanium alloy forming part is uniform in inside and complete in shape, and the strength of the titanium alloy is favorably improved.
Compared with the prior art, the invention has the following advantages:
1. according to the invention, the titanium alloy is prepared by adding iron powder to the Ti185 alloy powder to perform powder bed electron beam additive manufacturing, so that the growth restriction factor and the solidification temperature interval value of the alloy are improved, the formation of equiaxed crystals in the titanium alloy is facilitated, the beta/alpha transition temperature is reduced, the precipitation of a nano-alpha strengthening phase of the titanium alloy is promoted, the strength of the titanium alloy is improved, and the anisotropy of the mechanical properties of the titanium alloy is reduced.
2. According to the invention, the iron powder is added into the Ti185 alloy powder, and the addition amount is controlled according to the chemical element proportion calculation method, so that the formation of the medium axial crystals in the titanium alloy is promoted, the iron content in the mixed powder after the addition is within the component content range of the conventional Ti185 alloy powder, the introduction of other impurity elements is avoided, and the mechanical property of the titanium alloy is ensured.
3. According to the powder bed electron beam additive manufacturing process, the powder laying layer and the forming bottom plate are preheated, so that the gradual release of the internal thermal stress of the product titanium alloy is facilitated, the internal structure of the titanium alloy tends to be uniform, the adhesion among the powder is avoided, the binding force among titanium alloy layers is improved, the component segregation is avoided, and the mechanical properties such as the strength of the titanium alloy are further ensured.
4. According to the invention, by adding iron powder and combining with electron beam additive manufacturing of a powder bed, the prepared titanium alloy is isometric crystal inside, the strength is high, and the anisotropy of mechanical properties is obviously reduced, the tensile strength in the horizontal direction is higher than 1317MPa, the tensile strength in the vertical direction is higher than 1303MPa, the tensile yield strength in the horizontal direction is higher than 1241MPa, the tensile yield strength in the vertical direction is higher than 1222MPa, the elongation after fracture is higher than 5%, and the strength anisotropy value is not higher than 1.5, so that the titanium alloy can be made into a high-strength part, and the application range is wide.
The technical solution of the present invention is further described in detail by the accompanying drawings and examples.
Drawings
FIG. 1 is an optical microscope photograph of a titanium alloy prepared in example 1 of the present invention.
FIG. 2 is an optical microscopic view of a titanium alloy prepared in comparative example 1 of the present invention.
Detailed Description
The powder bed electron beam additive manufacturing apparatus used in examples 1 to 2 and comparative examples 1 to 2 of the present invention was of sialon Y150 type.
Example 1
The embodiment comprises the following steps:
step one, 1kg of spherical Ti185 alloy powder prepared by gas atomization of a plasma rotating electrode with the granularity of 40-150 microns is put into a ball milling tank, 18.9g of iron powder with the granularity of 1 micron is added, ball milling beads and ethanol are added, and ball milling is carried out for 4 hours at the rotating speed of 20r/min by adopting a planetary ball mill to obtain mixed powder; the spherical Ti185 alloy powder comprises the following components in percentage by mass: 1.38% of Al, 8.00% of V, 4.22% of Fe, 0.19% of O, and the balance of titanium and inevitable impurities;
secondly, drawing a three-dimensional model of a target product titanium alloy by adopting Magics software, wherein the size of the model is 80mm multiplied by 13mm multiplied by 22mm (length multiplied by width multiplied by height), then carrying out layering treatment, cutting the model into slices with the same thickness of 0.1mm along the height direction of the three-dimensional model, obtaining slicing data, and designing the internal scanning mode and the scanning path of each slice to obtain slicing scanning data; the slice scan data includes: the distance between the scanning lines is 0.1mm, the scanning current is 15mA, and the scanning speed is 3300mm/s;
step three, guiding the layer cutting data and the layer cutting scanning data obtained in the step two into powder bed electron beam additive manufacturing forming equipment, loading 8kg of mixed powder obtained in the step one into a powder box of the powder bed electron beam additive manufacturing equipment, leveling a forming bottom plate and preheating the forming bottom plate, wherein the preheating temperature of the forming bottom plate is 720 ℃, and the size of the forming bottom plate is 100mm multiplied by 10mm (length multiplied by width multiplied by thickness);
step four, laying the mixed powder filled into the powder box in the step three on the preheated forming bottom plate to form a powder laying layer with the thickness of 0.1mm, and then preheating the powder laying layer, wherein the preheating temperature of the powder laying layer is 720 ℃;
step five, according to the layer cutting data and the layer cutting scanning data which are led into the powder bed electron beam additive manufacturing forming equipment in the step three, melting and scanning the preheated powder laying layer in the step four by adopting an electron beam to form a single-layer solid sheet layer, and then lowering the forming bottom plate by 0.1mm; the process parameters of the melting scanning are as follows: the distance between scanning lines is 0.1mm, the scanning current is 15mA, and the scanning speed is 3300mm/s;
and step six, repeating the powder laying process and the preheating process in the step four and the melting scanning process and the forming bottom plate descending process in the step five until all the single-layer solid sheets are stacked layer by layer to form a powder bed electron beam additive manufacturing formed part, taking out the formed bottom plate when the temperature of the formed bottom plate is lower than 100 ℃, and removing residual powder on the surface of the powder bed electron beam additive manufacturing formed part by using high-pressure gas to obtain the high-strength titanium alloy.
Through detection, the tensile strength of the high-strength titanium alloy prepared in the embodiment in the horizontal direction is 1336MPa, the tensile yield strength is 1270MPa, the elongation after fracture is 9%, the tensile strength in the vertical direction is 1366MPa, the tensile yield strength is 1256MPa, the elongation after fracture is 6%, the anisotropy value of the tensile strength is 1.4, and the anisotropy value of the tensile yield strength is 1.1. Wherein the anisotropy value (IPA) is calculated according to formula (1).
In the formula (1), T H Represents the tensile or yield strength of the sample in the horizontal direction, in MPa; t is a unit of V The tensile or yield strength of the test specimen in the vertical direction is expressed in MPa.
Fig. 1 is an optical microscopic view of the titanium alloy prepared in this example, and it can be seen from fig. 1 that the titanium alloy is equiaxed crystal in the forming direction and has a fine α phase inside.
Comparative example 1
The comparative example differs from example 1 in that: this comparative example has no step one, i.e., no iron powder is added to the Ti185 alloy powder to obtain a Ti185 alloy.
Through detection, the tensile strength of the Ti185 alloy prepared by the comparative example in the horizontal direction is 1075MPa, the tensile yield strength is 1005MPa, the elongation after fracture is 17%, the tensile strength in the vertical direction is 1131MPa, the tensile yield strength is 1059MPa, the elongation after fracture is 6%, the anisotropy value of the tensile strength is 5.1, and the anisotropy value of the tensile yield strength is 5.2.
Fig. 2 is an optical microscopic view of the titanium alloy prepared in this comparative example, and it can be seen from fig. 2 that the titanium alloy has a columnar crystal structure in the forming direction.
Comparing example 1 with comparative example 1, the growth restriction factor and the solidification temperature interval of the Ti185 alloy powder which is not doped with the iron powder in comparative example 1 are lower, and the growth restriction factor of the Ti185 alloy (the iron mass content is 4.22%) is calculated to be 46.8, and the solidification temperature interval value is 96 ℃; in example 1, 1.89% of iron powder was added to the Ti185 alloy powder to form a mixed titanium alloy powder, which had a growth restriction factor of 66.6 (6% by mass of iron) and a solidification temperature range of 129 ℃. According to the theory of interdependence of solidification, the higher the growth-limiting factor and the solidification temperature interval, the more easily the equiaxed crystal is formed. Therefore, the titanium alloy obtained in example 1 has equiaxed crystals inside, while the titanium alloy obtained in comparative example 1 has columnar crystals inside, and the crystal grain size and the intracrystalline strengthening phase size of the equiaxed crystals are smaller than those of the corresponding columnar crystals, so that the strength of the titanium alloy is higher than that of the columnar crystals.
Comparative example 2
This comparative example differs from example 1 in that: in step one of the comparative example, 41.1g of iron powder was added, and the mass content of iron in the titanium alloy was 8%.
In the forming process of the powder bed electron beam additive manufacturing adopted in the comparative example, the powder flowability was poor and a large amount of spatter was generated in the forming process, resulting in the termination of the forming process.
Comparing example 1 with comparative example 2, it can be seen that the addition amount of the iron powder in comparative example 2 is 4.11%, the iron content in the titanium alloy is as high as 8% by mass, and the sphericity of the mixed powder is deteriorated due to the excessively high iron powder content, thereby reducing the fluidity. Meanwhile, as the difference between the melting point of iron and the melting point of Ti185 alloy exceeds 100 ℃, when the mass content of iron powder is increased, a great deal of splash is generated when the powder bed electron beam additive manufacturing technology is adopted for forming, the performance of a formed part is seriously influenced, and the forming process fails.
In conclusion, the invention improves the growth restriction factor and the solidification temperature interval value of the alloy by adding the iron powder into the Ti185 alloy powder and controlling the adding amount of the iron powder to be 6 percent, and simultaneously the mixed powder has good fluidity, thereby ensuring the forming process, promoting the formation of the mesoaxial crystals in the titanium alloy and further improving the strength of the titanium alloy.
Example 2
The embodiment comprises the following steps:
step one, 1kg of spherical Ti185 alloy powder prepared by gas atomization of a plasma rotating electrode with the granularity of 40-150 microns is put into a ball milling tank, 18.9g of iron powder with the granularity of 1 micron is added, ball milling beads and ethanol are added, and ball milling is carried out for 4 hours at the rotating speed of 20r/min by adopting a planetary ball mill to obtain mixed powder; the spherical Ti185 alloy powder comprises the following components in percentage by mass: 1.38% of Al, 8.00% of V, 4.22% of Fe, 0.19% of O, and the balance of titanium and inevitable impurities;
secondly, drawing a three-dimensional model of a target product titanium alloy by adopting Magics software, wherein the model size is 80mm multiplied by 13mm multiplied by 22mm (length multiplied by width multiplied by height), then carrying out layering treatment, cutting the model into slices with the same thickness of 0.1mm along the height direction of the three-dimensional model, obtaining slicing data, and designing the internal scanning mode and the scanning path of each slice to obtain slicing scanning data; the slice scan data includes: the distance between the scanning lines is 0.1mm, the scanning current is 15mA, and the scanning speed is 3300mm/s;
step three, guiding the layer cutting data and the layer cutting scanning data obtained in the step two into powder bed electron beam additive manufacturing forming equipment, loading 8kg of mixed powder obtained in the step one into a powder box of the powder bed electron beam additive manufacturing equipment, leveling a forming bottom plate and preheating the forming bottom plate, wherein the preheating temperature of the forming bottom plate is 700 ℃, and the size of the forming bottom plate is 100mm multiplied by 10mm (length multiplied by width multiplied by thickness);
step four, laying the mixed powder filled into the powder box in the step three on the preheated forming bottom plate to form a powder laying layer with the thickness of 0.1mm, and then preheating the powder laying layer, wherein the preheating temperature of the powder laying layer is 700 ℃;
step five, according to the layer cutting data and the layer cutting scanning data which are led into the powder bed electron beam additive manufacturing forming equipment in the step three, melting and scanning the preheated powder laying layer in the step four by adopting an electron beam to form a single-layer solid sheet layer, and then lowering the forming bottom plate by 0.1mm; the process parameters of the melting scanning are as follows: the distance between scanning lines is 0.1mm, the scanning current is 15mA, and the scanning speed is 3300mm/s;
and step six, repeating the powder laying process and the preheating process in the step four and the melting scanning process and the forming bottom plate descending process in the step five until all the single-layer solid sheets are stacked layer by layer to form a powder bed electron beam additive manufacturing formed part, taking out the formed bottom plate when the temperature of the formed bottom plate is lower than 100 ℃, and removing residual powder on the surface of the powder bed electron beam additive manufacturing formed part by using high-pressure gas to obtain the high-strength titanium alloy.
Through detection, the tensile strength of the high-strength titanium alloy prepared in the embodiment in the horizontal direction is 1317MPa, the tensile yield strength is 1241MPa, the elongation after fracture is 7%, the tensile strength in the vertical direction is 1303MPa, the tensile yield strength is 1222MPa, the elongation after fracture is 5%, the anisotropy value of the tensile strength is 1.1, and the anisotropy value of the tensile yield strength is 1.5.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modification, change and equivalent changes of the above embodiments according to the technical essence of the invention are still within the protection scope of the technical solution of the invention.
Claims (5)
1. A method for reducing anisotropy of mechanical properties of high-strength titanium alloy manufactured by additive manufacturing is characterized in that the high-strength titanium alloy with isotropic mechanical properties is prepared by increasing the iron content in Ti-1Al-8V-5Fe alloy, namely Ti185 alloy powder and adopting powder bed electron beam additive manufacturing, and the method comprises the following steps:
step one, adding iron powder into spherical Ti185 alloy powder prepared by plasma rotating electrode gas atomization, and then carrying out ball milling by adopting a planetary ball mill to obtain mixed powder;
drawing a three-dimensional model of a target product titanium alloy, then carrying out layering treatment, cutting the three-dimensional model into equal-thickness slices along the height direction of the three-dimensional model, obtaining slicing data, and designing the internal scanning mode and scanning path of each slice to obtain slicing scanning data;
step three, guiding the layer cutting data and the layer cutting scanning data obtained in the step two into powder bed electron beam additive manufacturing forming equipment, loading the mixed powder obtained in the step one into a powder box of the powder bed electron beam additive manufacturing equipment, leveling a forming bottom plate and preheating the forming bottom plate, wherein the preheating temperature of the forming bottom plate is 700-720 ℃;
step four, laying the mixed powder loaded into the powder box in the step three on the preheated forming bottom plate to form a powder laying layer, and then preheating the powder laying layer, wherein the preheating temperature of the powder laying layer is 700-720 ℃; the thickness of the powder laying layer is the same as that of the sliced sheet layer in the step three;
step five, according to the layer cutting data and the layer cutting scanning data which are led into the powder bed electron beam additive manufacturing forming equipment in the step three, melting and scanning the preheated powder laying layer in the step four by adopting an electron beam to form a single-layer solid sheet layer, and then descending the forming bottom plate, wherein the descending height of the forming bottom plate is the same as the thickness of the sheet layer which is divided in the step four;
step six, repeating the powder laying process and the preheating process in the step four and the melting scanning process and the forming bottom plate descending process in the step five until all the single-layer solid sheets are stacked layer by layer to form a powder bed electron beam additive manufacturing formed part, taking out the formed bottom plate when the temperature of the formed bottom plate is lower than 100 ℃, and removing residual powder on the surface of the powder bed electron beam additive manufacturing formed part by using high-pressure gas to obtain high-strength titanium alloy; the tensile strength of the high-strength titanium alloy in the horizontal direction is higher than 1317MPa, the tensile strength of the high-strength titanium alloy in the vertical direction is higher than 1303MPa, the tensile yield strength of the high-strength titanium alloy in the horizontal direction is higher than 1241MPa, the tensile yield strength of the high-strength titanium alloy in the vertical direction is higher than 1222MPa, the elongation after fracture is higher than 5%, and the strength anisotropy value is not higher than 1.5.
2. The method for reducing the anisotropy of mechanical properties of the additive manufactured high-strength titanium alloy according to claim 1, wherein in the first step, the spherical Ti185 alloy powder consists of the following components in percentage by mass: 1.38% of Al, 8.00% of V, 4.22% of Fe, 0.19% of O and the balance of titanium and inevitable impurities, and the particle size of the spherical Ti185 alloy powder is 40-150 μm.
3. The method for reducing the anisotropy of mechanical properties of high-strength titanium alloy manufactured by additive manufacturing according to claim 1, wherein the iron powder in the first step has a particle size of 1 μm and is added in an amount of 1.89% of the mass of the spherical Ti185 alloy powder.
4. The method for reducing the anisotropy of mechanical properties of the additive manufactured high-strength titanium alloy according to claim 1, wherein the thickness of the equal-thickness sheet layer in the second step is 0.1mm.
5. The method for reducing anisotropy of mechanical properties of additive manufactured high-strength titanium alloy according to claim 1, wherein the process parameters of the melting scan in the fifth step are as follows: the distance between scanning lines is 0.1mm, the scanning current is 15mA, and the scanning speed is 3300mm/s.
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